def calculate_crc7(data): """ Calculates CRC7 for the CID validation. Standard polynomial for MMC/SD is x^7 + x^3 + 1 (0x09). """ crc = 0 for byte in data: crc ^= byte << 8 for _ in range(8): if crc & 0x8000: crc ^= (0x12 << 8) # Poly 0x12 (inverted logic for calculation) crc <<= 1
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# Byte 15: CRC (CRC) crc_byte = raw_bytes[15] def calculate_crc7(data): """ Calculates CRC7 for the CID